mempolicy: reduce stack size of migrate_pages()

migrate_pages() is using >500 bytes stack. Reduce it.

   mm/mempolicy.c: In function 'sys_migrate_pages':
   mm/mempolicy.c:1344: warning: the frame size of 528 bytes is larger than 512 bytes

[akpm@linux-foundation.org: don't play with a might-be-NULL pointer]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 13 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 8a73708d59bb..f969da5dd8a2 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1275,33 +1275,42 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
                 const unsigned long __user *, new_nodes)
 {
         const struct cred *cred = current_cred(), *tcred;
-        struct mm_struct *mm;
+        struct mm_struct *mm = NULL;
         struct task_struct *task;
-        nodemask_t old;
-        nodemask_t new;
         nodemask_t task_nodes;
         int err;
+        nodemask_t *old;
+        nodemask_t *new;
+        NODEMASK_SCRATCH(scratch);
+
+        if (!scratch)
+                return -ENOMEM;
 
-        err = get_nodes(&old, old_nodes, maxnode);
+        old = &scratch->mask1;
+        new = &scratch->mask2;
+
+        err = get_nodes(old, old_nodes, maxnode);
         if (err)
-                return err;
+                goto out;
 
-        err = get_nodes(&new, new_nodes, maxnode);
+        err = get_nodes(new, new_nodes, maxnode);
         if (err)
-                return err;
+                goto out;
 
         /* Find the mm_struct */
         read_lock(&tasklist_lock);
         task = pid ? find_task_by_vpid(pid) : current;
         if (!task) {
                 read_unlock(&tasklist_lock);
-                return -ESRCH;
+                err = -ESRCH;
+                goto out;
         }
         mm = get_task_mm(task);
         read_unlock(&tasklist_lock);
 
+        err = -EINVAL;
         if (!mm)
-                return -EINVAL;
+                goto out;
 
         /*
          * Check if this process has the right to modify the specified
@@ -1322,12 +1331,12 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
 
         task_nodes = cpuset_mems_allowed(task);
         /* Is the user allowed to access the target nodes? */
-        if (!nodes_subset(new, task_nodes) && !capable(CAP_SYS_NICE)) {
+        if (!nodes_subset(*new, task_nodes) && !capable(CAP_SYS_NICE)) {
                 err = -EPERM;
                 goto out;
         }
 
-        if (!nodes_subset(new, node_states[N_HIGH_MEMORY])) {
+        if (!nodes_subset(*new, node_states[N_HIGH_MEMORY])) {
                 err = -EINVAL;
                 goto out;
         }
@@ -1336,10 +1345,13 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
         if (err)
                 goto out;
 
-        err = do_migrate_pages(mm, &old, &new,
+        err = do_migrate_pages(mm, old, new,
                 capable(CAP_SYS_NICE) ? MPOL_MF_MOVE_ALL : MPOL_MF_MOVE);
 out:
-        mmput(mm);
+        if (mm)
+                mmput(mm);
+        NODEMASK_SCRATCH_FREE(scratch);
+
         return err;
 }